package network;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TcpEchoServer {
    private ServerSocket serverSocket = null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        ExecutorService executorService = Executors.newCachedThreadPool();
        System.out.println("服务器启动！");
        while(true) {
            Socket clientSocket = serverSocket.accept();
            //如果直接用，该方法会影响这个循环的二次执行，导致 accept 不及时
            //创建新的线程，用新线程来调用 processConnection
            //每次来一个新的客户端都搞一个新的线程即可！
            /*Thread t = new Thread(() -> {
                try {
                    processConnection(clientSocket);
                } catch (IOException e) {
                    e.printStackTrace();
                }

            });
            t.start();
            */
            executorService.submit(new Runnable() {
                @Override
                public void run() {
                    try {
                        processConnection(clientSocket);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            });
        }
    }
    //通过这个方法来处理一个连接
    //读取请求
    //根据请求计算响应
    //把响应返回给客户端
    private void processConnection(Socket clientSocket) throws IOException {
        System.out.printf("[%s:%d] 客户端上线！\n",clientSocket.getInetAddress().toString(),
                clientSocket.getPort());
        // try() 这种写法，( ) 中允许写多个流对象，使用 ; 来分割
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()) {
            //没有这个 scanner 和 printWrite，完全可以！！但是代价就是得一个字节一个字节扣，找到哪个是请求的结束标记 \n
            //不是不能做，而是代码比较麻烦
            //为了简单，把字节流包装成了更方便的字符流
            Scanner scanner = new Scanner(inputStream);
            PrintWriter printWriter = new PrintWriter(outputStream);
            while (true) {
                //1.读取请求
                if(!scanner.hasNext()) {
                    //读取流到了结尾了（对端关闭了）
                    System.out.printf("[%s:%d] 客户端下线！\n",clientSocket.getInetAddress().toString(),
                            clientSocket.getPort());
                    break;
                }
                //直接使用 scanner 读取一段字符串
                String request = scanner.next();
                //2.根据请求计算响应
                String response = process(request);
                //3.把响应写回给客户端. 不要忘了，响应里也是要带上换行的.
                printWriter.println(response);
                printWriter.flush();
                System.out.printf("[%s:%d] req: %s; resp: %s\n",clientSocket.getInetAddress().toString(),
                        clientSocket.getPort(), request, response);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            clientSocket.close();
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer tcpEchoServer = new TcpEchoServer(9090);
        tcpEchoServer.start();
    }
}
